State;
Key;
Laboratory;
of;
Geological;
Processes;
and;
Mineral;
Resources,;
China;
University;
of;
Geosciences,;
Wuhan;
430074,China;
Key;
Laboratory;
of;
Continental;
Dynamics,;
Department;
of;
Geology,;
Northwest;
University,;
Xi'an;
710069,;
China;
State;
Key;
Laboratory;
of;
Geological;
Processes;
and;
Mineral;
Resources,;
China;
University;
of;
Geosciences,;
Wuhan;
430074,China;
Key;
Laboratory;
of;
Continental;
Dynamics,;
Department;
of;
Geology,;
Northwest;
University,;
Xi'an;
710069,;
China;
State;
Key;
Laboratory;
of;
Geological;
Processes;
and;
Mineral;
Resources,;
China;
University;
of;
Geosciences,;
Wuhan;
430074,China;
State;
Key;
Laboratory;
of;
Geological;
Processes;
and;
Mineral;
Resources,;
China;
University;
of;
Geosciences,;
Wuhan;
430074,China;
Key;
Laboratory;
of;
Continental;
Dynamics,;
Department;
of;
Geology,;
Northwest;
University,;
Xi'an;
710069,;
China;
Precambrian; mafic; volcanics,; Nb/Ta; deficit,; Archean-Proterozoic; boundary.;